goext/mongoext/projections.go
2023-05-05 18:22:15 +02:00

31 lines
689 B
Go

package mongoext
import (
"go.mongodb.org/mongo-driver/bson"
"reflect"
"strings"
)
// ProjectionFromStruct automatically generated a mongodb projection for a struct
// This way you can pretty much always write
// `options.FindOne().SetProjection(mongoutils.ProjectionFromStruct(...your_model...))`
// to only get the data from mongodb that you will actually use in the later decode step
func ProjectionFromStruct(obj interface{}) bson.M {
v := reflect.ValueOf(obj)
t := v.Type()
result := bson.M{}
for i := 0; i < v.NumField(); i++ {
tag := t.Field(i).Tag.Get("bson")
if tag == "" {
continue
}
tag = strings.Split(tag, ",")[0]
result[tag] = 1
}
return result
}